衰落信道下卷积码的软判决译码

本文将交织、信道输出软信息、信道特征软信息相结合,研究Rayleigh衰落信道下卷积码的Viterbi软判决译码,在利用和不利用信道状态信息(CSI)两种情况下给出软判决的支路度量计算公式和性能仿真结果,计算了卷积码的性能上界;研究了解调器输出量化门限(量化级数目、量化间距)对译码性能的影响.结果与硬判决译码及AWGN信道的相关结论进行了比较.     

Rician衰落信道下空时分组码的性能分析

基于Alamouti提出的BPSK调制下空时分组码在Rayleigh衰落信道中的码性能原理,推导出高阶(M ary)调制下Rician衰落信道中空时分组码的符号差错率的最小距离球界,并进行计算机仿真分析了两信道下引入空时分组码的多天线系统中发射和接收天线的分集增益,发射天线数量的“地板效应”以及Rician因子K对符号差错性能的影响。     

Rayleigh衰落信道中分组码最大似然译码的性能

摆脱了传统代数译码方法,对分组码进行基于广义阵列码（ＧＡＣ）结构的网格译码（Ｔｒｅｌｌｉｓ ｄｅｃｏｄｉｎｇ）,研究了Ｒａｙｌｅｉｇｈ衰落信道中分组码与这种软判决最大似然译码方法相结合的性能。模拟结果显示。分组码采用网格译码,可为移动衰落信道带来显著的性能改善。     

瑞利衰落信道上的6PSK环码

本文在文献「１０」的基础上，进一步探讨６ＰＳＫ环码在瑞利衰落信道上的误码特性，用分量码重量集合给出了衰落条件下误码概率指数Δ的表达式，并通过例子与相同构造条件下的陪集码进行了比较，证明了在瑞利衰落条件下，环码也优于任何一种构造的陪集码。     

衰落信道下多级编码方案的软判决译码

研究Rayleigh衰落信道下,软判决译码对三种不同映射方案多级编码系统性能的影响.基于信道容量规则,构造卷积码为分量码的8ASK多级编码系统,在多阶段译码中提出利用信道状态信息的软判决支路度量计算公式,并探讨系统的误码传播特性,研究结果可为衰落信道编码调制方案的最佳设计度量提供参考.     

瑞利信道下基于广义阈值函数的LDPC译码算法

现存的LDPC译码算法,其节点处理依据主要遵循大数逻辑准则和完全处理准则,对应的阈值参数一般是固定不变的,在性能和复杂度之间的均衡不够灵活.本文首先提出一种广义阈值函数,能应用于大多数基于可靠度的二元LDPC译码算法.通过调整阈值参数,可方便地控制参与迭代处理的节点队列.其次,本文提出一种基于伴随式和星座映射信息的非均匀量化译码算法,可进一步降低复杂度和存储负荷.实验结果显示,在瑞利信道下,本文算法能够在较低的量化比特下获得优良的译码性能;结合广义阈值函数,只有约30%的变量节点参与迭代运算,译码复杂度可显著降低.     

瑞利信道下的自适应MLSE算法

由于在数字移动通信中要考虑多径和多普勒频移的影响,建立了瑞利时变衰落信道模型,并使用最大似然序列检测算法实现均衡.它的基本思想是在MLSE算法中插入信道估计算法,不断跟踪实时信道变化并及时更新.为降低复杂度,研究了传统的自适应MLSE算法和运幸存MLSE两种经典算法,仿真表明,当多普勒频移较小时,两种算法有相近的性能,...     

多载波码分多址系统在瑞利衰落信道中的性能分析

多载波码分多址(MC-CDMA)是一种把多载波和CDMA相结合的技术方案。在MC-CDMA中,每个数据符号通过N个子载波传输,且根据扩频码对每个子载波以0或π相位偏移进行编码。分别研究了MC-CDMA系统上行链路和下行链路的瑞利衰落信道模型以及采用等增益组合和最大比组合的接收机模型,并对上行链路和下行链路的系统误码率性能进行了分析和计算。数值结果表明,MRC在上行链路中的性能要优于EGC,但在下行链路中的抗干扰性能不如EGC。     

基于遗传算法的卷积码快速译码

本文提出基于遗传算法(GA)的卷积码快速译码,进行格图上的单向(U-GA)和双向(B-GA)搜索译码.它利用遗传算法的群体多样性好、搜索空间宽广,具有全局优化能力,提高译码质量.通过模拟计算,分析了单向和双向的译码算法和群体规模M对误比特性能P_b的影响.模拟结果表明:在相同译码复杂度下、P_b=10^-6时,与MA算法(编码约束度K=19)相比,该译码算法约有0.5dB性能增益;与VA算法(K=7)相比,B-GA大约有1dB增益.     

A Simple Capacity Formula for Correlated Diversity Rayleigh Fading Channels

1　Introduction　Itiswellknownthatthesystemcapacitycanbeincreasedifweexploittherandomnessofmultipathpropagationappropriately .ThecapacityofMultiple InputMultiple Output (MIMO )isdiscussedinRef.[1 ].Ingeneral,theaveragechannelcapacitydependsonthecharacteristicsoffadingchannelsmostly .Andmostpaperonlyconsiderstheindepen dentandidenticallydistributedGaussianchannelvariable ,underthisassumption[2～3] ,havederived ,respectively ,theaverageandlimitingchannelcapac ity .　Theaimofthispaperistodet…     

适用于Rayleigh衰落信道的一种新型MMSE接收机

智能天线中一般的MMSE接收机缺乏有效跟踪Rayleigh衰落信道变化的机制。在分析了MMSE接收机在Rayleigh信道中的特点之后，提出了一种新型的MMSE接收机。计算机仿真结果表明，此接收机性能较好，适用于Rayleigh衰落信道。     

低密度校验码量化译码研究

介绍了基于置信传播算法的LDPC码和积译码算法，分析其密度进行化特性，对不同消息空间中的量化译码问题进行研究，对采用不同量化方案时LDPC码在AWGN信道下的译码性能进行了仿真。仿真结果表明相对连续译码，中间变量6bit均匀量化会带来约0．4dB左右的损失，而10bit非均匀量化性能明显得到改善。合适的高阶量化译码可以获得接近连续译码的性能。     

瑞利衰落信道MDPSK相位比较解调性能

本文提出一种适合于瑞利衰落信道多进制差分相移键控系统相位比较解调的性能分析方法，推导出符号错误率解析表示式，考虑了瑞利衰落、时间选择性衰落和高斯白噪声对体制性能的影响，并针对衰落功率谱为高斯型和矩形分别对二进制、四进制和八进制情形进行了数值计算。     

Error Probability Distribution and Density Functions for Rayleigh and Rician Fading Channels with Diversity

This paper analyzes the distribution and density functions of the probability of error for Rayleigh and Rician fading channels with diversity. An expression for the signal-to-noise ratio is derived for an asynchronous CDMA (A-CDMA) system with diversity. The error probability distribution and density functions are derived and plotted for different mean energy-to-noise ratios.

Combined Space Diversity Reception and Trellis Coding for Rayleigh Fading Channels

Space diversity reception, in which several signals received at different antennas are combined, is a well known method that can be used to combat the effects of fading in wireless systems. Also, trellis coded modulation (TCM), when combined with interleaving of sufficient depth, is known to provide some form of time diversity that allows the achievement of good error performance in fading environments. In this paper we consider the analysis of the error performance of reference-based Maximal Ratio Combining (MRC) systems when used in conjunction with trellis-coded MPSK modulation techniques over a Rayleigh fading channel. We also consider the analysis of MRC trellis-coded MPSK systems with conventional differential detection. The results are obtained by using a combination of theoretical analysis and simulation. Exact and near-exact expressions for the pairwise error-event probability in Rayleigh fading are derived. Monte-Carlo simulation results, which are more indicative of the exact system performance, are also given.     

瑞利衰落信道下扩频信号隐分集性能分析

介绍了瑞利衰落信道下采用扩频信号的失真接收机获取隐分集增益机理.在多重分集通道和每个分集通道存在离散多径的瑞利信道模型基础上,分别详细分析推导了单重分集通道和多重分集通道情况下的隐分集性能表达式,给出了不同情况下的误码性能理论曲线,并在硬件系统测试平台上,对扩频信号的隐分集性能进行了实测.测试结果表明该分析方法可行,可用于指导工程实践.     

Turbo Decoding of Super-Orthogonal Space-Time Trellis Codes in Rayleigh Fading Channels

Space-time trellis codes have shown to provide a good performance in Rayleigh fading channels. Recently Super-orthogonal space-time trellis codes have shown to outperform these codes, and also provide a systematic design method to maximize diversity and coding gain in quasi-static Rayleigh fading channels. We investigate the performance of these new codes in rapid Rayleigh fading channels and further propose two concatenated versions of these codes. We further investigate the effect of imperfect channel state information on one of the concatenated versions. Some simulation results of the various concatenated schemes in quasi-static and rapid Rayleigh fading channels are presented. Jayesh N. Pillai received the B.Tech degree in Electrical and Electronic Engineering from the University of Calicut, Kerala, India in 2001. He is currently pursuing an MScEng degree in Electronic Engineering at the School of Electrical, Electronic and Computer Engineering at the University of KwaZulu-Natal, Durban, South Africa. His research interests are in the area of wireless communications, including multiple-antenna systems, space-time coding and channel coding. Stanley Henry Mneney obtained his B.Sc.(Hons) Eng. Degree from the University of Science and Technology, Kumasi in Ghana in 1976. In 1979 he completed his M.A.Sc. from the University of Toronto in Canada. In a Nuffic funded project by the Netherlands government he embarked on a sandwich Ph.D. programme between the Eindhoven Univesity of Technology and the University of Dar es Salaam, the latter awarding the degree in 1988. His co-supervisors were Prof Jens Arnbak and Prof Ramje Prasad representing the two Universities. The research area was on the application satellite technology to provide low cost systems and services to the rural population in the developing countries.Prof Mneney has taught at the Universities of Dar es Salaam, Nairobi, Durban Westville and he is currently an Associate Professor and Deputy Head of School of Electrical, Electronic and Computer Engineering at the University of KwaZulu-Natal in South Africa. His research interest includes Signal and Image processing, radio propagation and communication systems.     

一种准静态平坦衰落信道下空时编码设计的新方法

空时码在准静态平坦瑞利衰落信道下的设计准则被广泛采用的是秩准则和行列式准则,但这些准则并不是很紧的。为此,提出了准静态平坦瑞利衰落信道下一种新的更紧的设计准则,采用这种准则还大大降低了穷举搜索空时好码的复杂度,仿真结果表明,搜索得到的空时好码性能优于现有的其它好码。     

Link Adaptation Based on Explicit Channel Estimation for Throughput Maximization Over Rayleigh Fading Channels

Link Adaptation (LA) has been proposed in the literature as a means of increasing the throughput obtained by each user in wireless communication systems. Due to its significant simplicity, LA has even been adopted as the standard adaptive coding technique for the next generation mobile communication system known as EDGE. In this paper, we present a novel link adaptation technique, valid for use in the case of Rayleigh fading wireless channels. The new technique is based on the blind channel estimation algorithm usually used for combating inter-symbol interference (ISI). The algorithm is presented and its efficiency in providing the maximum available throughput is illustrated by means of computer simulations.     

多序列跳频系统及其在瑞利衰落信道下性能分析

差分跳频中,用户数据对频率选择的约束性比较弱。对此本文提出多序列跳频（MSFH）系统,其发送频率不仅是用户数据的函数,也受同步跳频序列严格约束,因此可以采用窄带接收更好地抑制带外干扰。具体地,数据分组从一簇相互正交的跳频序列中选出一个序列,该序列的当前频率由射频端直接发送,而无需对发送信号进行调制。得到了瑞利衰落信道中,未编码和采用卷积编码-硬/软判决Viterbi译码时MSFH符号误码率性能。计算和仿真表明,在相同编码增益下,MSFH误码率低于常规跳频系统;与差分跳频译码复杂度相当时,MSFH性能亦具有一定优势。